Junction Field-Effect Transistor (JFET) is a type of field-effect transistor that can be used as an electronically-controlled switch or as a voltage-controlled resistor. In a JFET, electric charges flow through a semiconducting channel between a source and drain. By applying a bias voltage to a gate, the channel of the JFET may be pinched, so that the electric current flowing between the source and the drain is impeded or switched off.
JFETs have various structures. The different structures of the JFETs were design to suit for different usages of the JFETs. For example, the JFETs may be designed to be applied with high drain voltages, high currents, or the like.